#6 - Space affects the microbiome
Inside of each of our guts lives a vast community of microorganisms, known as the microbiome, which plays an important role in our overall health. To study how living in a microgravity environment impacts the
microbiome, Fred Turek of Northwestern University monitored the state of each twin’s microbiome before, during, and after the yearlong mission.
The researchers found that the microbiomes of both Scott and Mark were drastically different at all times throughout the project, but the differences were somewhat expected considering microbiomes are very sensitive to environmental variances such as diet and individual immunity. However, the researchers point out that Scott’s microbiome was different in space than it was preflight, displaying a decreased presence of one branch of bacteria known as
Bacteroidetes. However, these changes did not persist upon Scott’s return to Earth.
Even though the study showed that Scott’s microbiome changed when switching settings between Earth and space, the changes that were observed were similar to those that would be expected if someone on the ground significantly modified their diet or was exposed to a new environment.
#7 - Spaceflight can trigger gene mutations
Chris Mason of Weill Cornell Medicine used the Twins Study as an opportunity to investigate how space travel can influence
genetics. By looking for chemical changes in RNA and DNA through the use of whole-genome sequencing, the researchers showed that Scott experienced hundreds of unique gene mutations compared with his twin.
Though some distinct gene mutations were to be expected, even in twins, the sheer amount of changes surprised the researchers. A few of the gene changes, which were discovered only after Scott returned to Earth, were even found on cell-free DNA and RNA that was circulating in his bloodstream. The researchers believe that these gene changes resulted from the stresses of space travel, which can alter the biological pathways within cells, causing them to eject DNA and RNA. These free-floating DNA and RNA molecules can then trigger the production of new fats or proteins, or even turn specific genes on and off. Though 93 percent of the genes that expressed themselves differently while Scott was in space returned to normal postflight, the researchers found a subset of several hundred “space genes” that remained disrupted after his return.
Of the many gene-induced changes Scott’s body experienced, the researchers found five to be of particular relevance for future missions: (1) Hypoxia, which was likely caused by a lack of oxygen and a surplus of carbon dioxide; (2) Mitochondrial stress and increased levels of mitochondria in the blood, which suggests damage was done to the “power plants” of cells; (3) Telomere lengthening, DNA repair, and DNA damage, which could be a result of living a healthy lifestyle while constantly exposed to radiation; (4) Decreased collagen production, blood clotting, and bone formation, which was likely a combined result of living in microgravity and of fluids shifting around within the body; and (5) Hyperactive immune activity, which may be an effect of living in a new environment.
#8 - Living in space changes how genes are expressed
Similar to the previous project, Andy Feinberg of Johns Hopkins University conducted a study that tracked how each of the twins’
epigenetics (the way that genes express themselves) differed based on their environment.
In two separate populations of white blood cells, Feinberg found multiple regions of the genome where DNA methylation — the process responsible for turning genes on and off — had occurred. These chemical modifications to Scott’s genome were found near two interesting regions. One was close to a gene known to help regulate telomere growth, and another was found near a gene related to collagen production.
Although Scott did experience epigenetic changes during his time in space, the researchers found that the majority of changes were within the expected range of variability for his twin on Earth. However, the results related to telomere growth and collagen production are consistent with the findings of other Twins Study projects.
#9 - Artery walls thicken while in space
Stuart Lee of KBRWyle at NASA Johnson Space Center’s Cardiovascular and Vision Lab performed a study on how inflammation and oxidative stress (damage by free radicals in the air) can impact the structure and effectiveness of
arteries. To do this, the researchers examined the twins’ arteries using ultrasound, as well as collected blood and urine samples throughout the mission.
Both during and immediately after the mission, the researchers found that Scott’s inflammation biomarkers were elevated and that the wall of his carotid artery was thicker than it was preflight. Neither of these changes were seen in Mark during his stay on Earth.
At this point, the researchers do not know whether the thickening of Scott’s carotid artery is a temporary and reversible adaptation to living in space, or if it is evidence of permanent and premature arterial aging. Further study is needed to put these findings into clearer focus.
#10 - Proteins that regulate fluids increase while in space
In order to investigate how spaceflight impacts the body’s ability to form and modify
proteins, Brinda Rana of the University of California carried out a study that collected urine samples from Scott and Mark before, during, and after the mission. This allowed Rana to identify certain biomarker proteins that are associated with space-related bodily changes, such as muscle and bone loss, metabolic and cardiovascular changes, and the altered regulation of fluids within the body.
The researchers found that while Scott was in space, he excreted some proteins at different concentrations than his Earth-bound brother Mark. In particular, Scott had elevated levels of a protein called
aquaporin 2, which helps form the pathways used to carry water through cell membranes in the kidneys. Because aquaporin 2 helps regulate how water is transported within the body, it also serves as a valuable indicator of a body’s overall hydration status.
Notably, the researchers also found that Scott’s increase in aquaporin 2 during spaceflight was correlated with higher levels of plasma sodium — an indicator of dehydration. Though further study is needed, the researchers believe that the increase in aquaporin 2 and plasma sodium may be tied to fluids shifting throughout Scott’s body while he was in a microgravity environment. This is important because, as has been documented with other space-bound astronauts, fluids tend to migrate to the head, causing visual impairment and intracranial pressure.